AU2019429374A1

AU2019429374A1 - Sewing machine

Info

Publication number: AU2019429374A1
Application number: AU2019429374A
Authority: AU
Inventors: Mitsuru Sato
Original assignee: Suzuki Manufacturing Co Ltd
Current assignee: Suzuki Manufacturing Co Ltd
Priority date: 2019-02-15
Filing date: 2019-07-23
Publication date: 2021-05-20
Also published as: JP2020130369A; US20210404100A1; JP6555629B1; US11639569B2; WO2020166107A1; KR20210123286A; TW202031960A; DE112019006864T5; KR102596680B1; CN113195820A; CN113195820B; TWI821350B

Abstract

Provided is a sewing machine such that, when the feed dogs are retracted, the feed dogs can be located at an adequate distance below the upper surface of the throat plate. Feed dogs 3 protrude and sink from a throat plate 1. A horizontal feed driving part 8 converts the rotation of a drive shaft 7 into a reciprocating motion in the horizontal direction and transmits the same to the feed dogs 3. A vertical driving part 9 converts the rotation of the drive shaft 7 into a reciprocating motion in the vertical direction and transmits the same to the feed dogs. A vertical position-modifying part moves the turn-back points P at both ends of the outgoing path and the return path when the feed dogs 3 reciprocate in the horizontal direction below the throat plate 1.

Description

DESCRIPTION

Title of the Invention

SEWING MACHINE

Technical Field

[0001] The present invention relates to a sewing machine used for sewing products made of cloth.

Background Art

[0002] This type of sewing machine has feed dogs for feeding cloth on a throat plate

pressed by a presser foot. The feed dogs elliptically move by reciprocating in a horizontal

direction in a cloth feed direction and in a vertical direction with respect to the upper surface

of the throat plate in a sewing process.

[0003] More specifically, the feed dogs repeat a process in which the feed dogs advance forward in the cloth feed direction when the feed dogs move above the throat plate, retract

at a position below the throat plate, and move above the throat plate again. In this case, the forward feed of the cloth by the feed dogs is performed when a needle is in the vicinity

of a top dead center position. Therefore, the feed dogs are operated synchronously so as

to protrude from the upper surface of the throat plate when the needle is raised.

[0004] Meanwhile, before a sewing operation is started, the presser foot is raised and

cloth is set at an initial position of the sewing operation. At this time, the needle is at the

raised position, so that the feed dogs are in a state of protruding from the upper surface of

the throat plate. If the cloth is positioned below the needle in this state, the cloth comes

in contact with the feed dogs protruding from the upper surface of the throat plate, leading

to a possibility of interfering with smooth preparation for the sewing operation.

[0005] Thus, there has been proposed a feed dog lowering mechanism (refer to, for

example, Patent Literature 1 given below) adapted to lower the feed dogs from the upper

surface of the throat plate when the presser foot is raised before the sewing operation is

begun.

[0006] The feed dog lowering mechanism disclosed in Patent Literature 1 has an eccentric cam provided on a drive shaft, a lifting and lowering link connected, through a square piece, to a rod extending from the eccentric cam, and a guide member equipped with a guide groove that guides the square piece, and is configured to interlock the rotation of the guide member with a presser operation lever that separates the presser foot above the throat plate.

[0007] According to the configuration, when the presser foot is raised by operating the

presser operation lever, the guide member rotates and the guide groove, which guides the

square piece, tilts. The square piece moves along the tilted guide groove, thereby enabling

the feed dogs to move to a position below the upper surface of the throat plate (a retracted

position). Thus, the feed dog lowering mechanism disclosed in Patent Literature 1 can

retract the feed dogs by the simple configuration.

Citation List

Patent Literature

[0008] Patent Literature 1: Japanese Examined Utility Model Application Publication

No. 1-35729

Summary of Invention

Technical Problem

[0009] Meanwhile, feed dogs preferably move a sufficient distance in the state of

protruding from the upper surface of a throat plate when moving forward to feed cloth.

On the other hand, when the feed dogs switch from forward movement to backward

movement, if the feed dogs are positioned above the upper surface of the throat plate even

for a short period of time, there is a possibility that the retracting feed dogs will interfere

with the forward feed of the cloth. For this reason, the positions of the turn-back points

at both ends of a forward path and a return path for the feed dogs to reciprocate in a

horizontal direction are set to be slightly below the upper surface of the throat plate.

[0010] However, if the feed dog lowering mechanism disclosed in the aforesaid Patent

Literature 1 is adopted, there is a possibility that the feed dogs in a retracted state are

inconveniently positioned above the upper surface of the throat plate due to a setting error of the amount of protrusion of the feed dogs from the upper surface of the throat plate, the dimensional errors of components, or the like.

[0011] To prevent the problem described above, if the positions of the turn-back points

of the feed dogs are set below the upper surface of the throat plate with a relatively large

distance, then the amount of protrusion of the feed dogs from the upper surface of the throat

plate will be small, leading to a possibility that cloth cannot be sufficiently fed.

[0012] In view of the above, an object of the present invention is to provide a sewing

machine capable of reliably feeding cloth by feed dogs during a sewing operation and

positioning the feed dogs sufficiently below the upper surface of a throat plate when the

feed dogs are retracted.

Solution to Problem

[0013] To this end, a sewing machine in accordance with the present invention includes:

feed dogs which protrude and retract from an upper surface of a throat plate; a presser foot

which faces the top of the feed dogs; a drive shaft which transmits the power of a drive

source; a horizontal feed drive unit which converts a rotation of the drive shaft into a

reciprocating motion in a horizontal direction and transmits the reciprocating motion in the

horizontal direction to the feed dogs; a vertical drive unit which converts a rotation of the

drive shaft into a reciprocating motion in a vertical direction and transmits the reciprocating

motion in a vertical direction to the feed dogs; a vertical travel distance changing part which

changes a reciprocating travel distance of the feed dogs in the vertical direction; and a

vertical position changing part which moves turn-back points at both ends of a forward path

and a return path at the time of horizontal reciprocating travel of the feed dogs to be below

the upper surface of the throat plate in the case where the vertical travel distance changing

part decreases a vertical travel distance of the feed dogs.

[0014] The sewing machine according to the present invention is provided with the

vertical position changing part, thus making it possible to move the turn-back points at both

ends of the forward path and the return path at the time of the horizontal reciprocating travel

of the feed dogs to be below the upper surface of the throat plate. With this arrangement, when the feed dogs are retracted, the turn-back points can be positioned sufficiently below the upper surface of the throat plate by the vertical position changing part.

[0015] Further, in the sewing machine according to the present invention, the vertical

drive unit includes: an eccentric cam which is rotated by the drive shaft; an advancing and

retreating arm which is moved forward and backward in the horizontal direction by the

eccentric cam; a lifting and lowering link which has a lower end thereof connected to the

advancing and retreating arm through a lower connecting shaft and an upper end thereof

connected to a feed base which supports the feed dogs through an upper connecting shaft

such that the feed dogs can move in the horizontal direction; a square piece provided

coaxially with the lower connecting shaft of the lifting and lowering link; a guide member

having a guide groove formed therein to linearly guide the square piece; and a rotating shaft

which rotatably supports the guide member, the vertical travel distance changing part

includes a guide member rotating mechanism which rotates the guide member to change a

tilt angle of the guide groove, thereby changing the travel distance of the feed dogs in a

state of protrusion from the throat plate, the vertical position changing part is configured

by placement in which the rotating shaft of the guide member and the center of a

reciprocating travel region of the square piece in the guide groove are shifted away from

each other, and the center of the reciprocating travel region of the square piece is positioned,

being shifted to be lower than the rotating shaft of the guide member when the guide

member is rotated by the guide member rotating mechanism to cause the guide groove to

tilt.

[0016] According to the vertical drive unit having the aforesaid configuration, the

rotation of the drive shaft is converted through the eccentric cam into the horizontal

advancing and retreating motion of the advancing and retreating arm. The advancing and

retreating motion of the advancing and retreating arm causes the square piece to reciprocate

along the guide groove of the guide member. The lower end of the lifting and lowering

link is connected to the square piece through the lower connecting shaft, and the upper end

of the lifting and lowering link is connected to the feed base through the upper connecting

shaft. With this arrangement, the lifting and lowering link swings when the square piece

reciprocates along the guide groove, and the feed base is moved up and down by the swing

of the lifting and lowering link.

[0017] Regarding the relationship between the inclination of the guide groove and the

vertical motion of the feed dogs, the feed dogs move up and down the most when, for

example, the guide groove is horizontal. As the guide groove gradually tilts down in the

advancing direction of the advancing and retreating arm, the vertical motion of the feed

dogs becomes smaller while the horizontal travel distance thereof remains unchanged. In

other words, when a tilt is imparted so that the guide groove is tilted down in the advancing

direction of the advancing and retreating arm by rotating the guide member, the feed dogs

do not move up and down even when the drive shaft rotates (perform only the horizontal

reciprocating motion).

[0018] At this time, in the vertical position changing part, the rotating shaft of the guide

member and the center of the reciprocating travel region of the square piece in the guide

groove are positioned so as to be shifted away from each other. This shift causes the center

of the reciprocating travel region of the square piece to be positioned lower than the rotating

shaft of the guide member when the guide groove is in a tilted state. With this arrangement, when the guide groove is tilted, the feed dogs can be reliably retracted below the upper

surface of the throat plate by lowering the turn-back points of the feed dogs.

Brief Description of Drawings

[0019] FIG. 1 is an explanatory diagram illustrating the configuration of an essential

section of a sewing machine in an embodiment according to the present invention;

FIG. 2 is an explanatory diagram illustrating the configuration of a vertical drive

unit;

FIG. 3 is an explanatory diagram illustrating the configuration of a guide

member;

FIG. 4 is an explanatory diagram illustrating the configuration of an essential

section of a guide member rotating mechanism;

FIG. 5 is an explanatory diagram illustrating a state of an essential section during

a sewing operation;

FIG. 6 is an explanatory diagram illustrating the state of the essential section at

the time of retraction;

FIG. 7 is an explanatory diagram illustrating the comparison in configuration

between a rotating shaft in the guide member with eccentricity and the same without

eccentricity;

FIG. 8 is an explanatory diagram illustrating a positional relationship between

the trajectory of feed dogs and a throat plate during the sewing operation;

FIG. 9 is an explanatory diagram illustrating another positional relationship

between the trajectory of the feed dogs and the throat plate during the sewing operation;

and

FIG. 10 is an explanatory diagram illustrating a positional relationship between

the trajectory of the feed dogs during the sewing operation and the feed dogs at the time of

the retraction.

Description of Embodiments

[0020] An embodiment of the present invention will be described with reference to the

accompanying drawings. Although the illustration of the overall configuration is omitted, a sewing machine of the present embodiment is provided with a sewing needle (not

illustrated) which vertically reciprocates, a throat plate 1 on which the cloth of clothing or

the like is placed, a presser foot 2 which presses the cloth on the throat plate 1, and feed

dogs 3 which protrude and retract from the upper surface of the throat plate 1 to feed the

cloth, as illustrated in FIG. 1, as the configuration according to the gist of the present

invention.

[0021] The feed dogs 3 are driven by a feed dog drive unit. The feed dog drive unit

has a feed rod 4 extending in the horizontal direction, and a feed base 5 which supports the

feed rod 4 in a longitudinally movable manner. The feed dogs 3 are integrally provided

on the distal end of the feed rod 4.

[0022] The feed base 5 has the proximal end thereof connected to a frame (not

illustrated) through a swing shaft 6 so as to be vertically swingable. As the feed base 5

swings, the feed dogs 3 at the distal end of the feed rod 4 move in the vertical direction.

Further, the feed dog drive unit has a drive shaft 7 which transmits the power of a drive

source (not illustrated), a horizontal feed drive unit 8, and a vertical drive unit 9. The drive shaft 7 is provided below the feed base 5. The drive source also drives the sewing needle.

[0023] The horizontal feed drive unit 8 has a first eccentric cam 10 which is rotated by

the drive shaft 7, a first advancing and retreating arm 11 which is advanced and retreated

in the horizontal direction by the first eccentric cam 10, and an advancing and retreating

link 12 which transmits the advancing and retreating motion of the first advancing and

retreating arm 11 to the feed rod 4. The rotation of the drive shaft 7 is converted into a

horizontal feed motion by the horizontal feed drive unit 8 configured as described above

and the horizontal feed motion is transmitted to the feed dogs 3.

[0024] The vertical drive unit 9 is adapted to convert the rotation of the drive shaft 7 into

a vertical motion and transmit the vertical motion to the feed dogs 3, and includes a second

eccentric cam 13, a second advancing and retreating arm 14 which is advanced and

retreated in the horizontal direction by the second eccentric cam 13, and a lifting and

lowering link 15 connected to the second advancing and retreating arm 14, as illustrated in

FIG. 1 and FIG. 2. The second eccentric cam 13 corresponds to the eccentric cam in the

present invention, and the second advancing and retreating arm 14 corresponds to the

advancing and retreating arm in the present invention.

[0025] The lifting and lowering link 15 has the lower end thereof connected to the second

advancing and retreating arm 14 through a lower connecting shaft 16, and the upper end

thereof connected to the feed base 5 through an upper connecting shaft 17, as illustrated in

FIG. 2. A square piece 18 is provided at the lower end portion of the lifting and lowering

link 15 so as to be coaxial with the lower connecting shaft 16.

[0026] The square piece 18 is slidably accommodated in a guide groove 20 formed in a

guide member 19. The guide member 19 is disposed on one side (the right side in FIG.

2) of the drive shaft 7 and directly under the feed base 5. Because of the position where

the guide member 19 is disposed, the lifting and lowering link 15 is connected between the

swing shaft 6 in the feed base 5 and the feed dogs 3. This enables the vertical motion of

the lifting and lowering link 15 to be smaller than in the case where the leading end of the

feed dogs 3 is lifted and lowered.

[0027] As illustrated in FIG. 3, the guide member 19 has a round body block 22 rotated by a rotating shaft 21 supported by a frame (not illustrated).

[0028] The guide groove 20 is formed on one surface of the body block 22. The body

block 22 has an extended member 23 extending outward in the radial direction from one

portion thereof. A return spring 24 is connected to the extended member 23. The return

spring 24 is installed between the extended member 23 and a frame (not illustrated).

[0029] Further, the body block 22 is restricted, by a stopper pin 25 coming in contact

with the extended member 23, in counterclockwise rotation in FIG. 3 from the position at

which the guide groove 20 takes a horizontal attitude. The return spring 24 urges the body

block 22 in a return direction (the counterclockwise direction) when the body block 22

rotates in the clockwise direction in FIG. 3.

[0030] The simple configuration of the guide member 19 enables the guide member 19

to be installed without any problem even in a relatively narrow space such as directly under

the feed base 5. Consequently, a vertical drive unit 9 has a compact configuration.

[0031] In addition, the rotating shaft 21 is provided such that the center thereof is

eccentric with respect to the center of the round body block 22. The relationship among

the eccentric rotating shaft 21, the tilt of the guide groove 20 caused by the rotation of the

guide member 19, and the reciprocating travel region of the square piece 18 creates the

configuration for obtaining the function as the vertical position changing part in the present

invention. This configuration will be described in detail later.

[0032] As illustrated in FIG. 4, the guide member 19 is rotated by operating a presser

operation lever 26. The presser operation lever 26 is adapted to be raised and lowered to

lift and lower the presser foot 2 (refer to FIG. 1). The presser operation lever 26 and the

presser foot 2 are connected with each other through a link mechanism (not illustrated) for

making the up and down movement of the presser foot 2 follow the up and down operation

of the presser operation lever 26.

[0033] More specifically, in a state in which the presser operation lever 26 is down, the

presser foot 2 is in a state of pressure-contact with cloth on the feed dogs 3, and in a state

in which the presser operation lever 26 is up, the presser foot 2 is in a state of being

separated from the cloth on the feed dogs 3.

[0034] Further, as illustrated in FIG. 4, the guide member 19 is connected to the presser operation lever 26 through a rotating link 27. The rotating link 27 has a first link part 28 which follows the up and down movement of the presser operation lever 26, a transmission shaft 29 which converts the vertical motion of the first link part 28 into rotation and transmits the rotation, and a second link part 30 which transmits the rotation of the transmission shaft 29 to the extended member 23 of the guide member 19. The rotating link 27 is the guide member rotating mechanism in the present invention and constitutes, together with the presser operation lever 26, the vertical travel distance changing part in the present invention.

[0035] When the presser operation lever 26 is positioned at the lower end of the

operation range thereof, the guide groove 20 of the guide member 19 is set to be horizontal

(or substantially horizontal) by the first link part 28, the transmission shaft 29, and the

second link part 30. Further, a function of the vertical travel distance changing part makes

it possible to adjust the tilt angle of the guide groove 20 of the guide member 19 according

to the operation angle of the presser operation lever 26.

[0036] As illustrated in FIG. 5, when the guide groove 20 of the guide member 19 is

horizontal, the direction in which the square piece 18 reciprocates becomes the horizontal

direction along the guide groove 20, so that the feed base 5 is lifted up and pulled down by

the lifting and lowering link 15 as the square piece 18 reciprocates. Consequently, the

vertical travel distance of the feed dogs 3 reaches a maximum and the feed dogs 3 move,

drawing an elliptical trajectory, to feed the cloth by the advancing motion when protruding

upward above the upper surface of the throat plate 1.

[0037] When the presser operation lever 26 is raised, the first link part 28 moves along

the longitudinal direction thereof, and the second link part 30 rotates the guide member 19

against the biasing of the return spring 24 as the transmission shaft 29 rotates. This causes

the guide groove 20 of the guide member 19 to tilt. The tilt of the guide groove 20 at this

time will be a tilt that causes gradual movement down in a direction in which the second

advancing and retreating arm 14 pushes out (rightward in the drawing).

[0038] As illustrated in FIG. 6, when the guide groove 20 of the guide member 19 tilts,

the upper end of the lifting and lowering link 15 does not vertically move even when the

square piece 18 reciprocates along the guide groove 20 in the tilted state. Consequently, the feed dogs 3 operate, drawing a linear trajectory in the horizontal direction, without a vertical motion. At this time, the feed dogs 3 are positioned below the upper surface of the throat plate 1, so that the feed dogs 3 do not interfere with the setting of cloth above the feed dogs 3 to prepare for a sewing operation.

[0039] Further, as described above, the rotating shaft 21 is provided such that the center

thereof is eccentric with respect to the center of the round body block 22, thus making it

possible to reliably retract the feed dogs 3 below the upper surface of the throat plate 1.

[0040] This will be described in detail by comparison with a case where the center of the

rotating shaft 21 is not eccentric with respect to the center of the body block 22.

[0041] In FIG. 7, a configuration OM without eccentricity is illustrated as a reference

example on the left side in the drawing, and a configuration NM with eccentricity, which is

the present embodiment, is illustrated on the right side in the drawing.

[0042] The square piece 18 reciprocates along the guide groove 20. At this time, the

longitudinal dimension of the guide groove 20 can be reduced by making the longitudinal

center of the guide groove 20 and a center Si of a reciprocating travel region W of the

square piece 18 coincide with each other, and the body block 22 can be consequently made

compact. Further, in this case, the center of the body block 22 and the longitudinal center

of the guide groove 20 coincide with each other.

[0043] As illustrated in FIG. 7, in the configuration NM of the present embodiment, the

center of the rotating shaft 21 is set eccentric with respect to the center of the body block

22, thereby causing the center S Iof the reciprocating travel region W of the square piece

18 to be shifted to the lowering side of the guide groove 20 so as to tilt farther than a center

S2 of the rotating shaft 21.

[0044] In the state in which the cloth is fed during a sewing operation, the feed dogs 3

move on the elliptical trajectory, moving above the upper surface of the throat plate 1 to

feed the cloth and moving below the upper surface of the throat plate 1 to go back to the

return position thereof. At this time, the feed dogs 3 move, drawing an elliptical trajectory

R with respect to the throat plate 1 as indicated by the relationship between the trajectory

of the feed dogs 3 and the throat plate 1 in FIG. 8.

[0045] Further, the turn-back points P at both ends of the forward path and the return path of the reciprocating travel of the feed dogs 3 in the horizontal direction are set to be very slightly below the upper surface of the throat plate 1. The trajectory of the feed dogs

3 in the retracted state becomes a linear trajectory that connects both turn-back points P.

In the configuration OM without eccentricity illustrated as a reference example in FIG. 7,

the center Si of the reciprocating travel region W of the square piece 18 and the center S2

of the rotating shaft 21 coincide with each other, so that the positions of the turn-back points

P of the feed dogs 3 during a sewing operation (a state in which cloth feed is being

performed) and the turn-back points P of the feed dogs 3 in the retracted state due to the tilt

of the guide groove 20 do not change.

[0046] Here, if it is assumed that the turn-back points P of the feed dogs 3 are undesirably

positioned slightly above the upper surface of the throat plate 1 as illustrated in FIG. 9 due

to an error of the height adjustment of the feed dogs 3 or a dimensional error of a component,

then the feed dogs 3 will protrude above the upper surface of the throat plate 1 even when

the feed dogs 3 are in the retracted state, preventing smooth setting of cloth under a sewing

needle in the case of the configuration OM without eccentricity illustrated in FIG. 7.

[0047] In contrast, according to the configuration NM with eccentricity of the present

embodiment illustrated in FIG. 7, the center S Iof the reciprocating travel region W of the

square piece 18 is shifted to the lowering side of the tilted guide groove 20 with respect to

the center S2 of the rotating shaft 21, thus generating a lowering allowance L (exaggerated

for convenience of explanation) between the lower connecting shaft 16 and the upper

connecting shaft 17 of the lifting and lowering link 15.

[0048] Consequently, turn-back points Pa of the feed dogs 3 in the retracted state can be

positioned below the turn-back points P of the feed dogs 3 during a sewing operation as

illustrated in FIG. 10 simply by rotating the guide member 19 by the rotating shaft 21 with

eccentricity so as to tilt the guide groove 20. Thus, cloth can be smoothly set under a

sewing needle when preparing for a sewing operation or the like.

[0049] In the present embodiment, the function as the vertical position changing part in

the present invention is obtained by setting the center of the rotating shaft 21 of the guide

member 19 to be eccentric with respect to the center of the round body block 22 of the

guide member 19. The function as the vertical position changing part can be obtained by the position of the center Si of the reciprocating travel region W of the square piece 18 being shifted more to the lowering side than the rotating shaft 21 of the guide member 19 when the guide groove 20 tilts.

[0050] Further, the present embodiment is configured such that the guide groove 20

becomes horizontal when the presser operation lever 26 is positioned at the lower end,

however, the present invention is not limited thereto. More specifically, the configuration

may alternatively be such that the guide groove 20 becomes horizontal when the presser

operation lever 26 is positioned at the upper end. In addition, the angle of the guide groove

20 during a sewing operation is not limited to horizontal, and can be set appropriately

according to the dimensions of parts or the like.

Description of Reference Numerals

[0051] 1 ... throat plate; 2 ... presser foot; 3 ... feed dogs; 5 ... feed base; 7 ... drive shaft;

8 .. .horizontal feed drive unit; 9 ... vertical drive unit; 13 ... second eccentric cam (eccentric

cam); 14 ... second advancing and retreating arm (advancing and retreating arm); 15

... lifting and lowering link; 16 ... lower connecting shaft; 17 ... upper connecting shaft; 18

... square piece; 19 ... guide member; 20 ... guide groove; 21 ... rotating shaft; 26 ... presser

operation lever (vertical travel distance changing part); 27 ... rotating link (guide member

rotating mechanism); P, Pa ... turn-back point; W .. .reciprocating travel region; and S2

... center of reciprocating travel region.

Claims

1. A sewing machine comprising: feed dogs which protrude and retract from an

upper surface of a throat plate; a presser foot which faces a top of the feed dogs; a drive

shaft which transmits power of a drive source; a horizontal feed drive unit which converts

a rotation of the drive shaft into a reciprocating motion in a horizontal direction and

transmits the reciprocating motion in the horizontal direction to the feed dogs; a vertical

drive unit which converts the rotation of the drive shaft into a reciprocating motion in a

vertical direction and transmits the reciprocating motion in the vertical direction to the

feed dogs; a vertical travel distance changing part which changes a reciprocating travel

distance of the feed dogs in the vertical direction; and a vertical position changing part

which moves turn-back points at both ends of a forward path and a return path at the time

of a horizontal reciprocating travel of the feed dogs to be below the upper surface of the

throat plate in a case where the vertical travel distance changing part decreases a vertical

travel distance of the feed dogs.

2. The sewing machine according to claim 1,

wherein the vertical drive unit includes: an eccentric cam which is rotated by

the drive shaft; an advancing and retreating arm which is advanced and retreated in the

horizontal direction by the eccentric cam; a lifting and lowering link which has a lower

end thereof connected to the advancing and retreating arm through a lower connecting

shaft and an upper end thereof connected to a feed base which supports the feed dogs

through an upper connecting shaft such that the feed dogs can move in the horizontal

direction; a square piece provided coaxially with the lower connecting shaft of the lifting

and lowering link; a guide member having a guide groove formed therein to linearly

guide the square piece; and a rotating shaft which rotatably supports the guide member,

the vertical travel distance changing part includes a guide member rotating

mechanism which rotates the guide member to change a tilt angle of the guide groove,

thereby changing the travel distance of the feed dogs in a state of protrusion from the

throat plate, the vertical position changing part is configured by placement in which the rotating shaft of the guide member and a center of a reciprocating travel region of the square piece in the guide groove are shifted away from each other, and the center of the reciprocating travel region of the square piece is positioned so as to be shifted to be lower than the rotating shaft of the guide member in a case where the guide member is rotated by the guide member rotating mechanism to cause the guide groove to tilt.